It is known to produce electricity from an on-board assembly comprising an engine and a circuit for producing electricity from an alternator driven by the engine.
For example, a refrigeration system for a truck or an air-conditioning system for a bus, may be powered by an electricity production circuit having an alternator that is driven by the diesel engine that propels the truck or the bus.
In such a refrigeration or air-conditioning system, the speed of the alternator varies over a relatively large range as a function of the engine speed, e.g. with a factor of 1:5, and this is accompanied by variation in the voltage delivered by the alternator.